Radio communication device and transmission power control method

ABSTRACT

A CRC judgment section  103  performs a CRC check on decoded data every transmission unit, and if there is an error in the data, updates a flag held in a flag holding section  106  from 0 to 1; an increment/decrement value calculation section  105  calculates a reference SIR increment/decrement value according to the state (0 or 1) of the flag; a reference SIR update section  107  adds the reference SIR increment/decrement value to the current reference SIR value to find a new reference SIR value; a comparison section  109  compares the received signal SIR value measured by an SIR measurement section  108  with the updated reference SIR value, and a transmission power control bit generation section  110  generates a transmission power control bit according to the result of the comparison.

TECHNICAL FIELD

The present invention relates to a radio communication apparatus andtransmission power control method.

BACKGROUND ART

In a CDMA (Code Division Multiple Access) mobile communication system,transmission power control is an important technology from thestandpoint of expanding system capacity. One transmission power controlmethod is the outer loop transmission power control method. With theouter loop transmission power control method, mobile station apparatusesand a base station apparatus vary the reference SIR (Signal toInterference Ratio) according to quality that varies according to thepropagation environment in order to maintain the receiving line quality(abbreviated to “quality” below), such as the FER (Frame Error Rate) forexample, at a constant level, and transmission power control isperformed in accordance with the result of comparing that variablereference SIR with the reception SIR. The reason for varying thereference SIR so that mobile station apparatuses and the base stationapparatus maintain quality at a constant level is that, sincetransmission of excessive quality causes a slight increase ininterference with other stations, it is necessary to transmit at theminimum transmission power that satisfies the required quality.

A conventional radio communication apparatus that performs outer looptransmission power control will be described below. FIG. 1 is aprincipal block diagram showing the outline configuration of thereception system of a conventional radio communication apparatus. InFIG. 1, a demodulation section 11 performs predetermined demodulationprocessing on a received signal. A decoding section 12 decodes dataafter demodulation.

A CRC judgment section 13 performs a CRC (Cyclic Redundancy Check) ondecoded data, judges whether or not there is an error in the data, andoutputs data after judgment in decoding units. If an error is detected(if CRC=NG), an increment/decrement value calculation section 14generates a reference SIR increment value S1, expressed by equation (1)below. If an error is not detected (if CRC=OK), the increment/decrementvalue calculation section 14 generates a reference SIR decrement valueS2, expressed by equation (2) below. $\begin{matrix}{{S1} = {0.5\lbrack{dB}\rbrack}} & (1) \\\begin{matrix}{{S2} = {{- {S1}}*{FER\_ TARGET}\text{/}}} \\{\left( {1 - {FER\_ TARGET}} \right)\lbrack{dB}\rbrack} \\{{FER\_ TARGET} = 10^{- 3}\left( {{in}\quad{case}\quad{of}\quad{voice}\quad{communication}} \right)} \\{= 10^{- 4}\left( {{in}\quad{case}\quad{of}\quad{data}\quad{communication}} \right)}\end{matrix} & (2)\end{matrix}$

Equations (1) and (2) above are computational equations generally usedas reference SIR increment/decrement value computational equations inouter loop transmission power control. FER_TARGET indicates the FrameError Rate (quality) that it is wished to maintain at a constant levelfor the radio communication apparatus.

A reference SIR update section 15 updates the reference SIR value byadding a reference SIR increment/decrement value determined by aboveequation (1) or (2) to the current reference SIR value. The update cycleis generally the CRC judgment cycle of 10 ms. The updated reference SIRvalue is output to a comparison section 17.

The comparison section 17 compares the received signal SIR valuemeasured by an SIR measurement section 16 with the updated reference SIRvalue, and outputs the result of the comparison to a transmission powercontrol bit generation section 18. If the measured SIR value is largerthan the reference SIR value, the transmission power control bitgeneration section 18 generates a transmission power control bitdirecting the communicating party to decrease transmission power. If themeasured SIR value is equal to or smaller than the reference SIR value,the transmission power control bit generation section 18 generates atransmission power control bit directing the communicating party toincrease transmission power.

The transmission power control bit generation section 18 then outputsthe generated transmission power control bit to the transmission systemof the radio communication apparatus. In the transmission system, thetransmission power control bit is mapped onto the transmit signal. Thecommunicating party adjusts the transmission power according to thereceived transmission power control bit. Conventionally, outer looptransmission power control is performed in this way between radiocommunication apparatuses.

However, there is a problem with the conventional radio communicationapparatus and outer loop transmission power control method, as follows.

FIG. 2 is a drawing showing variations in the reference SIR when outerloop transmission power control is performed using a conventional radiocommunication apparatus. FIG. 2 shows the case of an 80 ms decoding unitand 10 ms frame: that is, the case where eight CRC judgments (1) to (8)are performed at 10 ms intervals within 80 ms. Time is shown on thehorizontal axis and reference SIR values on the vertical axis.

If an error is detected in CRC judgments (3) to (5) (if CRC=NG), areference SIR increment value S1 is calculated with equation (1) above.That is to say, in CRC judgments (3) to (5) the reference SIR values areeach incremented by 0.5 [dB].

If an error is not detected in CRC judgments (6) to (8) (if CRC=OK), areference SIR decrement value S2 is calculated with equation (2) aboveas shown below.S2=−0.5*10⁻⁴/(1−10⁻⁴)≈−{fraction (0.5/10000)} [dB]  (3)

where FER_TARGET=10⁻⁴ (in case of data communication)

That is to say, in CRC judgments (6) to (8) the reference SIR values areeach decremented by approximately {fraction (0.5/10000)} [dB].

As can be seen from the result of equation (3) above, the reference SIRvalues are decremented on an extremely gentle gradient. Therefore, witha conventional radio communication apparatus, once the receive dataquality becomes excessive, an extremely long time is required for thereference SIR value to be set to the optimum reference SIR value. Thatis, with a conventional radio communication apparatus, the time duringwhich data is transmitted at excessive transmission power is extremelylong, and therefore interference with other stations increases andsystem capacity decreases.

DISCLOSURE OF INVENTION

It is an objective of the present invention to provide a radiocommunication apparatus and transmission power control method that makeit possible to prevent a decrease in system capacity arising due toexcessive transmission power.

The inventors of the present invention perceived that the cause of thetime during which data is transmitted at excessive transmission powerbeing extremely long is that the difference between the reference SIRvalue increment width and the reference SIR value decrement width isextremely large.

In order to achieve the above-described objective, in the presentinvention the difference between the reference SIR value increment widthand the reference SIR value decrement width is considered in advance,the increment width is adjusted so that the reference SIR value does notincrease too much, and if the reference SIR value does increase toomuch, the decrement width is increased in accordance with the incrementwidth.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a principal block diagram showing the outline configuration ofthe reception system of a conventional radio communication apparatus;

FIG. 2 is a drawing showing variations in the reference SIR when outerloop transmission power control is performed using a conventional radiocommunication apparatus;

FIG. 3 is a principal block diagram showing the outline configuration ofthe reception system of a radio communication apparatus according toEmbodiment 1 of the present invention;

FIG. 4 is a flowchart for explaining the operation of the receptionsystem of a radio communication apparatus according to Embodiment 1 ofthe present invention;

FIG. 5 is a drawing showing variations in the reference SIR when outerloop transmission power control is performed using a radio communicationapparatus according to Embodiment 1 of the present invention;

FIG. 6 is a principal block diagram showing the outline configuration ofthe reception system of a radio communication apparatus according toEmbodiment 2 of the present invention;

FIG. 7 is a flowchart for explaining the operation of the receptionsystem of a radio communication apparatus according to Embodiment 2 ofthe present invention; and

FIG. 8 is a drawing showing variations in the reference SIR when outerloop transmission power control is performed using a radio communicationapparatus according to Embodiment 2 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described specificallybelow with reference to accompanying drawings.

(Embodiment 1)

A radio communication apparatus according to Embodiment 1 of the presentinvention increments the reference SIR value by a predetermined amountonce only within a decoding unit, and after performing the incrementonce, for subsequent frames decrements the reference SIR value by apredetermined amount even if there is deemed to be an error.

A radio communication apparatus and transmission power control methodaccording to Embodiment 1 of the present invention will be describedbelow. FIG. 3 is a principal block diagram showing the outlineconfiguration of the reception system of a radio communication apparatusaccording to Embodiment 1 of the present invention.

In FIG. 3, a demodulation section 101 performs predetermineddemodulation processing on a received signal. A decoding section 102performs decoding of data after demodulation. A CRC judgment section 103performs a CRC on the decoded data, judges whether or not there is anerror in the data, and outputs receive data after judgment in decodingunits. The number of CRC judgments to be performed per decoding unit isset in advance in a judgment count section 104. For example, if thedecoding unit is 80 ms and the transmission unit is 10 ms per frame, thenumber of CRC judgments is set as 8. The judgment count section 104 isfor counting the number of CRC judgments.

An increment/decrement value calculation section 105 calculates areference SIR increment/decrement value in accordance with the state (0or 1) of a flag held in a flag holding section 106. A reference SIRupdate section 107 holds the current reference SIR value. The referenceSIR update section 107 adds the reference SIR increment/decrement valuedetermined by the increment/decrement value calculation section 105 tothe current reference SIR value to find a new reference SIR value. Thereference SIR update section 107 then updates the current reference SIRvalue with that new reference SIR value, and outputs that updatedreference SIR value to a comparison section 109.

The comparison section 109 compares the received signal SIR valuemeasured by an SIR measurement section 108 with the updated referenceSIR value, and outputs the result of the comparison to a transmissionpower control bit generation section 110. If the measured SIR value islarger than the reference SIR value, the transmission power control bitgeneration section 110 generates a transmission power control bitdirecting the communicating party to decrease transmission power. It themeasured SIR value is equal to or smaller than the reference SIR value,the transmission power control bit generation section 110 generates atransmission power control bit directing the communicating party toincrease transmission power.

The transmission power control bit generation section 110 then outputsthe generated transmission power control bit to the transmission systemof the radio communication apparatus. In the transmission system, thetransmission power control bit is mapped onto the transmit signal. Thecommunicating party adjusts the transmission power according to thereceived transmission power control bit. In this way, outer looptransmission power control is performed between radio communicationapparatuses.

Next, the operation of the reception system of a radio communicationapparatus having the above-described configuration will be describedusing FIG. 4. FIG. 4 is a flowchart for explaining the operation of thereception system of a radio communication apparatus according toEmbodiment 1 of the present invention.

When decoded data is output from the decoding section 102 in decodingunits, first, in step (abbreviated to “ST” below) 201, the CRC judgmentsection 103 resets the number of CRC judgments i held in the judgmentcount section 104 to 0, and also resets a flag F held in the flagholding section 106 to 0. In the flowchart in FIG. 4, the number of CRCjudgments to be performed per decoding unit is indicated by “N”. In thefollowing description, the case is shown where the decoding unit is 80ms and the transmission unit is 10 ms per frame: that is, the case whereeight CRC judgments are performed at 10 ms intervals within 80 ms. Here,therefore, “N” has been set to 8 in advance in the judgment countsection 104. In the following description, “N” is called “the maximumnumber of CRC judgments.”

Next, in ST202, the CRC judgment section 103 increments by 1 the numberof CRC judgments i held in the judgment count section 104.

Then, in ST203, the judgment count section 104 compares the number ofCRC judgments i with the maximum number of CRC judgments N. If i N, thejudgment count section 104 directs the CRC judgment section 103 toperform CRC judgment for the i'th frame of decoded data in a decodingunit. In this case, the procedure advances to ST204.

If, on the other hand, i N is not true in ST203 (that is, if the numberof CRC judgments i exceeds the maximum number of CRC judgments N), thejudgment count section 104 directs the CRC judgment section 103 tooutput decoded data in decoding units. By this means, the CRC judgmentsection 103 outputs receive data every decoding unit.

Next, in ST204, the CRC judgment section 103 judges whether or not thereis an error in the decoded data, and outputs a signal indicating thepresence or absence of an error to the increment/decrement valuecalculation section 105.

If there is no error in ST204 (if CRC=OK), in ST205 theincrement/decrement value calculation section 105 generates a referenceSIR decrement value S2 in accordance with equations (4) and (5) below,and outputs the generated reference SIR decrement value S2 to thereference SIR update section 107. Following this, the procedure returnsto ST202, and the processing is repeated. $\begin{matrix}{{S1} = {0.5\lbrack{dB}\rbrack}} & (4) \\{{S2} = {{- {S1}}*{FER\_ TARGET}\text{/}{\left( {1 - {FER\_ TARGET}} \right)\lbrack{dB}\rbrack}}} & (5)\end{matrix}$

FER_TARGET indicates the Frame Error Rate (quality) that it is wished tomaintain at a constant level for the radio communication apparatus.FER_TARGET is generally set to 10⁻³ in the case of speech communicationand to 10⁻⁴ in the case of data communication.

If, on the other hand, there is an error in ST204 (if CRC=NG), in ST206the increment/decrement value calculation section 105 references thestate of the flag F held in the flag holding section 106. If F=0, theincrement/decrement value calculation section 105 updates F to 1 inST207, and then in ST208 generates a reference SIR increment value S1 inaccordance with equation (4) above, and outputs the generated referenceSIR increment value S1 to the reference SIR update section 107. If F=1,in ST205 the increment/decrement value calculation section 105 performsthe same processing as when there is no error (when CRC=OK). Theprocedure then returns to ST202, and the processing is repeated.

When the above operations are performed, after the flag F is set to 1,the reference SIR value continues to be decremented by the decrementwidth S2 even if there is an error(if CRC=NG). That is to say, within adecoding unit the reference SIR value is incremented by the incrementwidth S1 once only, and after being incremented once, the reference SIRvalue is decremented by the decrement width S2 even if an error occursin a subsequent frame. Therefore, looking at each decoding unit, thereference SIR value increment width is held down to S1 or below, andtherefore the reference SIR value rises on a gentler gradient than witha conventional radio communication apparatus and transmission powercontrol method, making it possible to reduce beforehand the extent towhich the receive data quality becomes excessive.

Next, variations in the reference SIR when outer loop transmission powercontrol is performed using a radio communication apparatus having theabove-described configuration will be described using FIG. 5. FIG. 5 isa drawing showing variations in the reference SIR when outer looptransmission power control is performed using a radio communicationapparatus according to Embodiment 1 of the present invention.

FIG. 5 shows the case of an 80 ms decoding unit and a transmission unitof 10 ms per frame: that is, the case where eight CRC judgments (1) to(8) are performed at 10 ms intervals within 80 ms. Time is shown on thehorizontal axis and reference SIR values on the vertical axis.

If an error is detected in CRC judgment (3) (if CRC=NG), the referenceSIR value is incremented by the increment width S1.

Following this, even if an error is detected (if CRC=NG) in CRC judgment(4) or (5) the reference SIR value is decremented by the decrement widthS2, since the reference SIR value has been incremented once within adecoding unit in CRC judgment (3).

Thus, in CRC judgments (1) to (8) within a decoding unit, incrementingof the reference SIR value by the increment width S1 is performed onceonly in CRC judgment (3), and in all CRC judgments other than CRCjudgment (3) the reference SIR value is decremented by the decrementwidth S2.

Now, above equations (4) and (5) used in this embodiment are onlyexamples, and the equations are not limited to these. Therefore, aboveequation (4) can be any equation as long as it is an equation expressinga reference SIR increment value. Also, above equation (5) can be anyequation as long as it is an equation expressing a reference SIRdecrement value.

Moreover, in this embodiment, incrementing of the reference SIR isperformed only once within a decoding unit. However, the number of timesthe reference SIR is incremented within a decoding unit is not limitedto this, and it is also possible to use a total of two or more incrementwidths per time for the reference SIR value.

Thus, according to this embodiment, within a decoding unit, incrementingof the reference SIR value by a predetermined amount is performed apredetermined number of times (for example, once) only, and afterincrementing is performed the predetermined number of times, thereference SIR value is decremented by a predetermined amount even ifthere is an error in a subsequent frame. Therefore, since the referenceSIR value rises on a gentler gradient than with a conventional radiocommunication apparatus and transmission power control method, it ispossible to reduce beforehand the extent to which the receive dataquality becomes excessive. As a result, it is possible to shorten thetime during which data is transmitted at excessive transmission power.

(Embodiment 2)

A radio communication apparatus according to this embodiment differsfrom a radio communication apparatus according to Embodiment 1 in that,within a decoding unit, the reference SIR value decrement width isvaried adaptively according to the number of times the reference SIRvalue is incremented by a predetermined amount.

A radio communication apparatus according to Embodiment 2 of the presentinvention will be described below. FIG. 6 is a principal block diagramshowing the outline configuration of the reception system of a radiocommunication apparatus according to Embodiment 2 of the presentinvention. The parts in FIG. 6 identical to those in FIG. 3 are assignedthe same numbers as in FIG. 3, and their detailed explanations areomitted.

In FIG. 6, a CRC judgment section 401 performs a CRC on decoded data,judges whether or not there is an error in the data, and outputs receivedata after judgment in decoding units. An increment/decrement valuecalculation section 402 calculates a reference SIR increment/decrementvalue in accordance with the number of errors within a decoding unitheld in an error count section 403.

Next, the operation of the reception system of a radio communicationapparatus having the above-described configuration will be describedusing FIG. 7. FIG. 7 is a flowchart for explaining the operation of thereception system of a radio communication apparatus according toEmbodiment 2 of the present invention. A detailed explanation of stepsfor which the operation is identical to that in 4 is omitted.

When decoded data is output from the decoding section 102 in decodingunits, first, in ST501, the CRC judgment section 103 resets the numberof CRC judgments i held in the judgment count section 104 to 0, andresets a counter C held in the error count section 403 to 1.

Next, in ST502, the CRC judgment section 401 increments by 1 the numberof CRC judgments i held in the judgment count section 104.

Then, in ST503, the judgment count section 104 compares the number ofCRC judgments i with the maximum number of CRC judgments N. If i N, thejudgment count section 104 directs the CRC judgment section 401 toperform CRC judgment for the i'th frame of decoded data in a decodingunit. In this case, the procedure advances to ST504.

If, on the other hand, i N is not true in ST503 (that is, if the numberof CRC judgments i exceeds the maximum number of CRC judgments N), thejudgment count section 104 directs the CRC judgment section 401 tooutput decoded data in decoding units. By this means, the CRC judgmentsection 401 outputs receive data every decoding unit.

Next, in ST504, the CRC judgment section 401 judges whether or not thereis an error in the decoded data, and outputs a signal indicating thepresence or absence of an error to the increment/decrement valuecalculation section 402.

If there is an error in ST504 (if CRC=NG), in ST505 the CRC judgmentsection 401 increments by 1 the counter C held in the error countsection 403. Then, in ST506, the increment/decrement value calculationsection 402 generates a reference SIR increment value S1 in accordancewith equation (4) above, and outputs the generated reference SIRincrement value S1 to the reference SIR update section 107. Followingthis, the procedure returns to ST502, and the processing is repeated.

If, on the other hand, there is no error in ST504 (if CRC=OK), in ST507the increment/decrement value calculation section 402 generates areference SIR decrement value S2′ in accordance with equation (6) below,and outputs the generated reference SIR decrement value S2′ to thereference SIR update section 107. The procedure then returns to ST202,and the processing is repeated.S 2′=C*S 2 expressed by above equation (5) [dB]  (6)

If there is no error in the decoded data (if CRC=OK) when the aboveoperations are performed, the reference SIR value is decremented by adecrement width that is in accordance with the number of errors detectedup to that time within a decoding unit. That is to say, the more timesthe reference SIR value has been incremented by a predetermined amount,the larger is the decrement width per time for the reference SIR value.Therefore, the reference SIR value falls at a steeper gradient than witha conventional radio communication apparatus and transmission powercontrol method, with the result that the time during which receive dataquality is excessive is greatly shortened compared with a conventionalradio communication apparatus and transmission power control method.

Now, above equation (6) used in this embodiment is only an example, andthe equation is not limited to this. Therefore, above equation (6) canbe any equation as long as it is an equation expressing the fact thatthe more times the reference SIR value has been incremented by apredetermined amount within a decoding unit, the larger is the referenceSIR decrement value.

Next, variations in the reference SIR when outer loop transmission powercontrol is performed using a radio communication apparatus having theabove-described configuration will be described using FIG. 8. FIG. 8 isa drawing showing variations in the reference SIR when outer looptransmission power control is performed using a radio communicationapparatus according to Embodiment 2 of the present invention.

FIG. 8 shows the case of an 80 ms decoding unit and a transmission unitof 10 ms per frame: that is, the case where eight CRC judgments (1) to(8) are performed at 10 ms intervals within 80 ms. Time is shown on thehorizontal axis and reference SIR values on the vertical axis.

If an error is detected in CRC judgments (3) to (5) (if CRC=NG), thereference SIR values are incremented by the increment width S1.

Following this, if an error is not detected in CRC judgments (6) to (8)(if CRC=OK), the reference SIR values are decremented by a decrementwidth S2′ that is in accordance with the number of errors detected up tothat time within a decoding unit. To be specific, in CRC judgments (6)to (8), the reference SIR value is decremented at a gradient four timesthat in the case of a conventional radio communication apparatus andtransmission power control method.

Thus, according to this embodiment, within a decoding unit the decrementwidth of the reference SIR value is varied adaptively according to thenumber of times the reference SIR value has been incremented by apredetermined amount, enabling the time during which receive dataquality is excessive to be greatly shortened compared with aconventional radio communication apparatus and transmission powercontrol method.

In above-described Embodiment 1 and Embodiment 2, SIR values are used asa reference value and measured values, but this is not a limitation.That is to say, any value, such as the reception level, for example, canbe used as a reference value and measured values, as long as it is avalue that indicates reception quality.

It is also possible for above-described Embodiment 1 and Embodiment 2 tobe implemented in combination.

Also, a radio communication apparatus according to above-describedEmbodiment 1 or Embodiment 2 can be applied to a communication terminalapparatus or base station apparatus in a mobile communication system.When applied, the time during which data is transmitted at excessivetransmission power by a communication terminal apparatus or base stationapparatus can be shortened, making it possible to prevent a decrease inthe system capacity of a mobile communication system.

According to the present invention, as described above, it is possibleto prevent a decrease in system capacity arising due to excessivetransmission power.

This application is based on the Japanese Patent Application No.HEI11-340727 filed on Nov. 30, 1999, entire content of which is expresslyincorporated by reference herein.

1. A radio communication apparatus comprising: a decoder that performsdecoding processing on reception data every decoding unit, saidreception data including a plurality of transmission units in saiddecoding unit; a judging unit that judges a presence or absence of anerror in the decoded reception data every transmission unit; an updaterthat increments or decrements a reference value of a reception qualityaccording to said presence or absence of an error to update saidreference value; and a generator that generates a transmission powercontrol bit according to a result of comparison of the updated referencevalue and a measured reception quality, wherein within each decodingunit, the number of times said updater increments said reference valueis less than the number of transmission units having an error.
 2. Theradio communication apparatus of claim 1, wherein, within each decodingunit, said updater increments said reference value only when an error isfirst detected.
 3. The radio communication apparatus of claim 1,wherein, within each decoding unit, said updater increments saidreference value only once.
 4. The radio communication apparatus of claim1, wherein said updater, after having incremented said reference value apredetermined number of times, decrements said reference value even whenthe transmission unit has an error.
 5. A communication terminalapparatus comprising the radio communication apparatus of claim
 1. 6. Abase station apparatus comprising the radio communication apparatus ofclaim
 1. 7. A radio communication apparatus, comprising: a decoder thatperforms decoding processing on reception data every decoding unit, saidreception data including a plurality of transmission units in saiddecoding unit; a judging unit that judges a presence or absence of anerror in the decoded reception data every transmission unit; an updaterthat increments or decrements a reference value of a reception qualityaccording to said presence or absence of an error to update saidreference value; and a generator that generates a transmission powercontrol bit according to a result of comparison of the updated referencevalue and a measured reception quality, wherein within each decodingunit, said updater decrements said reference value by a decrement widththat is in accordance with the number of times said reference value isincremented.
 8. The radio communication apparatus of claim 7, whereinsaid updater increases the decrement width proportionately as the numberof times said reference value is incremented increases.
 9. Acommunication terminal apparatus comprising the radio communicationapparatus of claim
 7. 10. A base station apparatus comprising the radiocommunication apparatus of claim
 7. 11. A transmission power controlmethod comprising: performing decoding processing on reception dataevery decoding unit, said reception data including a plurality oftransmission units in said decoding unit; judging a presence or absenceof an error in the decoded reception data every transmission unit;incrementing or decrementing a reference value of a reception qualityaccording to said presence or absence of an error to update saidreference value; and generating a transmission power control bitaccording to a result of comparison of the updated reference value and ameasured reception quality, wherein within each decoding unit, thenumber of times said reference value is incremented is less than thenumber of transmission units having an error.
 12. A transmission powercontrol method comprising: performing decoding processing on receptiondata every decoding unit, said reception data including a plurality oftransmission units in said decoding unit; judging a presence or absenceof an error in the decoded reception data every transmission unit;incrementing or decrementing a reference value of a reception qualityaccording to said presence or absence of an error to update saidreference value; and generating a transmission power control bitaccording to a result of comparison of the updated reference value and ameasured reception quality, wherein within each decoding unit, saidreference value is decremented by a decrement width that is inaccordance with the number of times said reference value is incremented.